My father passed away on Shabbat morning, 23/10/2010 which was 15 Chesvan. He was buried on 24/10/2010. As its a leap year , I am not sure when I stop Kaddish. Can you please advise

Shalom, Kaddish is recited for 11 months, as the punishment for the wicked in Gehenom is at most 12 months, and one does not want to proclaim that their parents were so wicked as to attain a full 12 months there. So even though the mourning is for one year, the kaddish is only for 11 months. You will recite your last kaddish on the 15th of Ellul (Wednesday the 14th of September 2011 - up to and including Mincha), which is the last day of 11 months of reciting kaddish, which you started on the 16th of Chesvan, on the day of the burial. Even though it was a leap year, we count the extra month as we would any other month, and so this does not affect the calculation of the 11 months of kaddish, nor the 12 months of mourning, which will end for you on the 15th of Tishrei (the first day of Succot). The Yahrzeit is determined from the date of death, not burial, that is for your father on the 15th of Cheshvan (and does not come after 12 months, but on the calendar date of the death). On that day (Wednesday, 31 Oct. 2012), you will recite kaddish again. May you be a merit to the memory of your father, Blessings.